HE STOOD nearly 8ft tall, earned his living from 'freak' shows and died at 22.

Now researchers have found that Charles Byrne, the most famous giant in medical history, sprang from a mutant gene that first appeared 1,500 years ago and is still causing excessive growth in families in the same area of Co Derry where he was born.

The current "race of giants" is concentrated in a small area, but researchers requested its location not be disclosed to protect residents from onlookers.

Following the discovery, doctors screened four families from the area and identified three patients in the early stages of excessive growth who had not realised they were affected.

The four families had given rise to half-a-dozen giants and others affected by growth abnormalities in recent generations.

Gigantism is caused by a benign tumour of the pituitary gland which produces excessive growth hormone. If it occurs early in life, it can cause a child to grow very tall. In adulthood it causes abnormal growth of the face, hands, feet and other parts of the body in the condition known as acromegaly.

Mr Byrne, born in 1761, grew rapidly in his teens and travelled to London at the age of 19 to seek his fortune. An etching from the period shows him with two men nearly as tall, who came from a village eight miles from his.

In the 1780s he found fame exhibiting himself as a curiosity or "freak".

Skeletal evidence shows his height to have been just over 7ft 7in. Celebrity life got the better of Mr Byrne, who took to drink and died aged just 22.

His skeleton remains at the Hunterian Museum at the London headquarters of the Royal College of Surgeons. Marta Korbonits, professor of endocrinology at the London School of Medicine, led the study, published in the 'New England Journal of Medicine'.

A new Irish language documentary exploring the life of Charles Byrne will air on BBC Two NI at 7pm on Sunday 16 January